1. Field of the Invention
The present invention relates generally to a method for manufacturing a multiple walled vessel that is capable of containing liquid even if the primary, secondary or any number of desired vessel walls is ruptured, up to the final or outermost containment wall.
2. Description of the Prior Art
Multiwalled containers are currently in use in numerous industries in the United States. These containers may serve any number of purposes, from providing insulation or temperature controlling effects, to safely containing harmful or hazardous materials, such as chemicals. Most multi-walled containers require a preformed inner shell to be disposed inside a preformed outer shell, thereby creating an space in between the two shells. Such a process can be costly and does not allow existing containers to be converted to use as multiwalled containers. Similarly, by combining preformed shells, it is difficult, expensive and sometimes impossible to create a multiwalled container in the shape needed for a specific application.
The present invention provides an improved method for creating a multiwalled vessel. The method may be used to convert an existing shell or structure from a single walled container into a multiwalled container, such as in the case of upgrading or rehabilitating an existing liquid storage vessel, or the method may be used to manufacture a completely new multi-walled container. Where a new container is manufactured, a mold or form may be used to shape the container appropriately for a given application.
Regardless of whether an existing shell or structure or a mold is being used the interior surface or substrate of the shell must be prepared prior to application liner material. Typically, the substrate surface will at least be thoroughly cleaned to remove any undesirable material, such as dirt, oxidation, corrosion or the like, from the surface which may prevent the liner material from properly adhering. Such preparation may include, for example, abrasive blasting or water jetting. Additional steps may be taken to further prepare the substrate surface for the application of liner material. For instance, the surface may be mechanically abraded or chemically etched to provide a desired surface profile in order to maximize adhesion of the liner material.
Once the substrate surface has been adequately cleaned and prepared, a first polymer layer may be applied. This first polymer layer is typically impermeable to the liquid that will be disposed in the container. Similarly, the first polymer layer will have some resistance against deterioration caused by the liquid in the container. The first layer forms a primer, bonding or anchor layer upon which subsequent materials may be applied. The first polymer layer may be formed using any suitable material. This first polymer layer will form the outermost containment wall of the container.
A second, interstitial layer of permeable, non-absorbing material may then be applied to the exposed inner surface of the first polymer layer. This interstitial layer will typically be applied to form voids or pockets throughout so that liquid may travel through the voids and collect at some point within the interstitial material. Additionally, the interstitial material may provide support for successive layers of material which may be applied. Monitoring devices may be located in the interstitial material for detecting the presence of liquid, such as in the case of a leak or rupture.
A third impermeable polymer layer may then be applied to the exposed inner surface of the interstitial layer. This third polymer layer is typically of the same composition as the first polymer layer, but may be formed from any suitable material. The third layer will form the interior of the container and will also form the primary containment wall. By forming the third layer over the second, interstitial layer, an interstitial space is formed between the first layer and the third layer, through which liquid may run should the third layer crack or rupture.
The present invention is particularly useful for restoring, repairing or rehabilitating existing liquid storage vessels and containers. The method provides a new and improved, multi-walled interior to the existing container, so that it can be either put back into full use or easily converted to use with a new or different liquid. In this way the useful life of the container may be significantly extended at a reduced cost.
Although the procedure described forms a double walled vessel or container, it should be understood that any number of additional layers may be included, depending on the specific application for which the container will be used.